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  • Solar Panel Hookup. Series or Parallel?

    Hi, I was wondering what would be the best way to hook up a solar panel system for maximum production. From what I understand it comes down to either series or parallel. Thank you.

    Jackie

  • #2
    Re: Solar Panel Hookup. Series or Parallel?

    Hello Jackie and thanks for joining Solar Panel Talk. I'll explain briefly what the two mean.

    Series wiring is when you connect a positive terminal from one solar panel and connect it to the negative of another. Doing this will result in higher voltage (the sum of voltage from the panels) while the amps stay the same.

    Parallel wiring is when you connect a positive with a positive and a negative to a negative. When you do this the voltage remains the same, meanwhile the you get higher amps. So two 12 volt/3.5 amp panels hooked up in parallel would output 12 volts at 7 amps. Four panels hooked together would produce 12 volts at 14 amps and so on.

    Hopefully that will help you in deciding which way you want to hook them up.

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    • #3
      so why would you want more voltage compared to amps and vice versa?

      Comment


      • #4
        Series or parallel

        Just to see this clearly....sorry to be a bit thick.....but does this mean one runs series to charge batteries, and parallel to run appliances directly?
        Thanks J.SUN

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        • #5
          Your module and inverter combination dictates how you should wire everything. These modules wired in series are called "strings." The number of modules per string is dictated by your inverter operating voltage window. For example, SMA inverters have a DC voltage window of between 250-600V. Your maximum number of modules per string is controlled by the module open circuit voltage (Voc) adjusted for your lowest record temperature (600v/Voc x NEC 690.7 correction factor). The minimum number of modules per string is controlled by the module max power voltage (Vmp) adjusted for your hottest record temperature. The Voc and Vmp correction factors are found on the module data sheet.

          It is always good practice to add 10-20% to your turn-on voltage to account for the drop in output that the modules will experience over 20-30 years (usually 10-20%).


          Once you have determined your number of modules per string, you then add strings in parallel. You do not want to add to many strings because your inverter can only produce power up to it's nameplate wattage (with a few exceptions). Basically you want to make sure your AC wattage is as close to your inverter rating as possible, so that you are not paying for DC watts not converted to AC electricity. It will not, however, damage the inverter to exceed its maximum usable current. You could have 1000 strings wired to a 2000w inverter and not damage it, as long as your number of modules per string falls into the inverter DC operating voltage range. The reason for this is that the inverter is able to "throttle" the current flowing through it with capacitors. Any power in excess of the inverter's capacity is simply not created.

          To determine your AC wattage: (#modules)x(module PTC wattage)x(inverter efficiency)

          Whew!

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          • #6
            I just also needed to add that all of your inverter manufacturers will have a string sizing tool availible on the internet that will tell you all of possible configurations.

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            • #7
              Great post above. I was just browsing the site and that ended up clearing up some things for me. Thanks!

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              • #8
                Enphase micro-inverters

                After reading this post I believe I understand that series wiring is the only way to go to get the most efficient energy generation when wiring solar panels!

                My question is: What about the Enphase Solar panel micro-inverter system? With each panel having its own micro-inverter would that not mean that each panel was wired in parallel?

                I was thinking about putting a dozen solar panels on the flat roof I have available and then over the next decade adding a couple of dozen more panels above the regular asphalt roofing (I'm hoping to protect the roofing from the direct solar radiation). Could I benefit from my investment over time using the above mentioned system? Also, would it be best to purchase a 36 panel trunk cable initially, even though the flat roof panels are going to be located 10 or 12 feet apart at their nearest adjacent locations?

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                • #9
                  Originally posted by Nathan in Forks View Post
                  After reading this post I believe I understand that series wiring is the only way to go to get the most efficient energy generation when wiring solar panels!

                  My question is: What about the Enphase Solar panel micro-inverter system? With each panel having its own micro-inverter would that not mean that each panel was wired in parallel?

                  I was thinking about putting a dozen solar panels on the flat roof I have available and then over the next decade adding a couple of dozen more panels above the regular asphalt roofing (I'm hoping to protect the roofing from the direct solar radiation). Could I benefit from my investment over time using the above mentioned system? Also, would it be best to purchase a 36 panel trunk cable initially, even though the flat roof panels are going to be located 10 or 12 feet apart at their nearest adjacent locations?
                  Using micro inverters is approximately like wiring your panels in parallel but now you are doing this at a higher AC voltage instead of the lower DC panel voltage. You still need to understand that even using micro inverters, you have a limit of how many can be connected on a "string" that goes to the circuit breaker in your panels so 36 may be too many.

                  Now the bad news. Once you have installed a system and get it approved by your POCO and AHJ you should be able to expand it but will probably need to submit new drawings for a new permit to get that approved before you add even micro inverters.

                  In the end it still comes down to the total amount of wattage allowed to be connected to your panel based on the panel buss and main circuit breaker rating. You will not be allowed to exceed a certain percentage based on the National Electric Code Article 690.

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                  • #10
                    I'm still working on the basics

                    I am still not an expert on solar panels nor the intricacies of their wiring, I do know that I don't want to wire up solar panels that cost energy and me money to hook them up to the grid, and I want to make sure of my wiring plan to be sure I am getting the most benefit
                    from the buck invested.

                    I know the Enphase system is the most expensive and simplest to use, but if it is possible to spend money on solar panels and wire them up in such a way that no benefit is obtained by adding solar panels, then we really need to study this subject in depth! The extra money I am willing to spend on the Enphase system I imagine benefits though simple wiring design, and safety in that if I lose one panel or inverter, I do not lose the whole shebang; However those benefits will not be worth paying even less money for if the Enphase system does not efficiently convert solar energy into marketable energy in a competitive manner in respect to all of the other alternatives on the market in the same price range. That is basically what I want to understand thouroughly. Can anyone answer this question and enlighten us in perhaps lay-mans terms and using simple examples?

                    Comment


                    • #11
                      Originally posted by Nathan in Forks View Post
                      I am still not an expert on solar panels nor the intricacies of their wiring, I do know that I don't want to wire up solar panels that cost energy and me money to hook them up to the grid, and I want to make sure of my wiring plan to be sure I am getting the most benefit
                      from the buck invested.

                      I know the Enphase system is the most expensive and simplest to use, but if it is possible to spend money on solar panels and wire them up in such a way that no benefit is obtained by adding solar panels, then we really need to study this subject in depth! The extra money I am willing to spend on the Enphase system I imagine benefits though simple wiring design, and safety in that if I lose one panel or inverter, I do not lose the whole shebang; However those benefits will not be worth paying even less money for if the Enphase system does not efficiently convert solar energy into marketable energy in a competitive manner in respect to all of the other alternatives on the market in the same price range. That is basically what I want to understand thouroughly. Can anyone answer this question and enlighten us in perhaps lay-mans terms and using simple examples?
                      Basically it comes down to how many kWh you want to generate and for what reasons. Some people install solar to cut their electric bill by reducing the amount of kWh by 60% of what they purchase from the Utility or POCO. Others want to generate 100% of their consumption and sell back the extra to their POCO depending on the type of Net metering contract they can get. How much you use and what your cost /kWh helps determine the length of time it takes for the system to pay for itself.

                      The type of equipment and pricing for that equipment has a wide range of selection depending on where you live and what you can get. IMO spending more money on a system that claims to have higher output and a longer warranty is usually a waste because you will not get back in kWh production to cover the extra amount you spend on the installation.

                      Most places in the US require a licensed Contractor to install the system or at least a licensed Electrician to make the final connections. Also some POCO's have a limit on the size of the pv system wattage based on their requirements.

                      So there is no simple answer to your question until you can provide some more data on where you live and who do you purchase your electricity from. That is the starting point.

                      Back to the original question by the OP. Wiring panels in series or parallel depends on the type of pv panel and inverter or charge controller you are using.
                      Last edited by SunEagle; 08-03-2015, 10:07 AM. Reason: added last sentence

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                      • #12
                        Right now just hoping to lower electric bill, but hoping for more in the future.

                        I have only limited resources to invest right now, and the most I am hoping for initially is to lower my electric bill. I found what I thought was a good deal on a set of 8 solar panels; being a new home owner with a bit of flat roof to work with as well as a significant electric bill with electric heating, I thought it would be a good idea so I purchased the set of 8. However, I would love to be able to generate all of my energy needs and even sell some back to the Grid if it is economically feasible down the road. Thus I am starting with 8 panels but can easily fit sixteen on the flat roof section of the house. I would even consider installing solar panels over the asphalt shingles if I thought it would significantly extend the life of the roof, but that is another matter. What I need to know is does the Enphase system competitively harness solar energy, and if so does it require one big trunk cable to do so? Thus I had better purchase the size trunk cable for my vision of the final sytem array perhaps sixteen panels if I just stick to the flat roof?

                        Comment


                        • #13
                          Originally posted by Nathan in Forks View Post
                          I have only limited resources to invest right now, and the most I am hoping for initially is to lower my electric bill. I found what I thought was a good deal on a set of 8 solar panels; being a new home owner with a bit of flat roof to work with as well as a significant electric bill with electric heating, I thought it would be a good idea so I purchased the set of 8. However, I would love to be able to generate all of my energy needs and even sell some back to the Grid if it is economically feasible down the road. Thus I am starting with 8 panels but can easily fit sixteen on the flat roof section of the house. I would even consider installing solar panels over the asphalt shingles if I thought it would significantly extend the life of the roof, but that is another matter. What I need to know is does the Enphase system competitively harness solar energy, and if so does it require one big trunk cable to do so? Thus I had better purchase the size trunk cable for my vision of the final sytem array perhaps sixteen panels if I just stick to the flat roof?
                          Nathan

                          I do not have first hand experience with the Enphase hardware or know how to size a system trunk line for future expansion.

                          I still encourage you to talk to a few solar pv installers to find out how much it costs / watt for them to install a system.

                          You could then check out what it would cost for you to purchase the equipment and install what you are allowed to but you also need to know what if any requirements you need to comply with to get it approved by your POCO or they will not purchase any of the excess power you generate.

                          Comment


                          • #14
                            Originally posted by Nathan in Forks View Post
                            I have only limited resources to invest right now, and the most I am hoping for initially is to lower my electric bill. I found what I thought was a good deal on a set of 8 solar panels; being a new home owner with a bit of flat roof to work with as well as a significant electric bill with electric heating, I thought it would be a good idea so I purchased the set of 8. However, I would love to be able to generate all of my energy needs and even sell some back to the Grid if it is economically feasible down the road. Thus I am starting with 8 panels but can easily fit sixteen on the flat roof section of the house. I would even consider installing solar panels over the asphalt shingles if I thought it would significantly extend the life of the roof, but that is another matter. What I need to know is does the Enphase system competitively harness solar energy, and if so does it require one big trunk cable to do so? Thus I had better purchase the size trunk cable for my vision of the final sytem array perhaps sixteen panels if I just stick to the flat roof?
                            When comparing inverters look at the weighted CEC figure in the data sheet.
                            This is the inverter efficiency rating. Almost all are above 95%.
                            With emphase you are limited to 17 on a string. So that will work for the initial.

                            Avoid the flat area it will cost more to install. The sloped shingle area if facing more or less south is best.
                            Last edited by Naptown; 08-04-2015, 09:36 AM.
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